feat(review): simplification specialist — advisory over-engineering lens with ponytail's tag vocabulary

New 8th Review Army specialist (DIFF_LINES > 100, --simplification force flag)
hunting unrequested STRUCTURE only: delete/stdlib/native/speculative/shrink
closed tags, one-line findings, lines_removable field. speculative: replaces
ponytail's yagni: tag — we import the lens, not the posture; coverage stays
sacred (Completeness Gaps owns it, suppressions inlined, shrink needs >=5 lines).

Advisory carve-out in the merge step: advisory findings are excluded from
quality_score and the findings-count header, render with an [ADVISORY] label,
and are ASK-only in Fix-First. Zero-findings case prints the lens-scoped
'Simplification: lean already — nothing to cut.' from the PARENT (the
specialist keeps the exact NO FINDINGS contract); with findings, the parent
prints 'net: -N lines possible' summed from lines_removable.

Tests: static pins for the carve-out + early-out contract (gen-skill-docs),
two periodic e2e cases with planted fixtures — activation (over-build traps:
hand-rolled Intl, one-impl abstract, dead config) and false-flag precision
(a lean ETHOS 'choose A' diff must yield NO FINDINGS).

Inspired by dietrichgebert/ponytail's /ponytail-review.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

review/checklist.md

@@ -7,7 +7,9 @@ Review the `git diff origin/main` output for the issues listed below. Be specifi
 **Two-pass review:**
 - **Pass 1 (CRITICAL):** Run SQL & Data Safety, Race Conditions, LLM Output Trust Boundary, Shell Injection, and Enum Completeness first. Highest severity.
 - **Pass 2 (INFORMATIONAL):** Run remaining categories below. Lower severity but still actioned.
-- **Specialist categories (handled by parallel subagents, NOT this checklist):** Test Gaps, Dead Code, Magic Numbers, Conditional Side Effects, Performance & Bundle Impact, Crypto & Entropy. See `review/specialists/` for these.
+- **Specialist categories (handled by parallel subagents, NOT this checklist):** Test Gaps, Dead Code, Magic Numbers, Conditional Side Effects, Performance & Bundle Impact, Crypto & Entropy, Simplification (unrequested structure). See `review/specialists/` for these.
+
+Completeness Gaps and Simplification are orthogonal, not contradictory: Completeness pushes coverage UP (tests, edge cases, error paths), Simplification pushes unrequested structure DOWN (one-implementation abstractions, hand-rolled stdlib, dead flexibility). The same diff can legitimately receive both.
 
 All findings get action via Fix-First Review: obvious mechanical fixes are applied automatically,
 genuinely ambiguous issues are batched into a single user question.
@@ -129,8 +131,8 @@ CRITICAL (highest severity):      INFORMATIONAL (main agent):      SPECIALIST (p
 ├─ Shell Injection                ├─ LLM Prompt Issues             ├─ Performance specialist
 └─ Enum & Value Completeness      ├─ Completeness Gaps             ├─ Data Migration specialist
                                    ├─ Time Window Safety            ├─ API Contract specialist
-                                   ├─ Type Coercion at Boundaries   └─ Red Team (conditional)
-                                   ├─ View/Frontend
+                                   ├─ Type Coercion at Boundaries   ├─ Simplification (advisory)
+                                   ├─ View/Frontend                 └─ Red Team (conditional)
                                    └─ Distribution & CI/CD Pipeline
 
 All findings are actioned via Fix-First Review. Severity determines